Reddening maps of the Magellanic Clouds

We present reddening maps of the Large and Small Magellanic Clouds, based on color measurements of the red clump stars.


Empirical calibration of the reddening maps in the Magellanic Clouds

M. Górski, B. Zgirski, G. Pietrzyński, W. Gieren, P. Wielgórski, D. Graczyk, R.-P. Kudritzki, B. Pilecki, W. Narloch, P. Karczmarek, K. Suchomska, M. Taormina

2020, eprint arXiv:2001.08242

Interstellar dust is the most important source of the errors of the distance measurements. As the effect of absorption and scattering on the dust particles, observed colors of the stars tend to shift toward red. This phenomena is known as the reddening, and can be directly used to calculate amount of the brightness of the stars that is obscured by interstellar dust.

In their last paper, Dr. Gorski with coauthors presented high-resolution maps of the reddening in the Large and Small Magellanic Clouds. To obtain these maps, authors used OGLE III photometric maps to trace the change of color of the red clump stars – objects that should have the same color no matter where they are located within the galaxy. To obtain the color excess of the red clump stars, authors had to measure first, what is the natural, unreddened color of the red clump stars. To do this they used four different methods; and by doing so they secured very precise value.

Reddening map of the LMC. Measurements were performed in 3 × 3 arcmin fields. The color bar indicates reddening value E(B−V) [mag].
Reddening map of the SMC. Measurements were performed in 3 × 3 arcmin fields. The color bar indicates reddening value E(B−V) [mag].

The Large Magellanic Cloud and Small Magellanic Cloud are dwarf galaxies, located in the proximity of Milky Way. They are important objects to study large variety of astrophysical phenomena and play a crucial role for the distance scale, as the distances to both galaxies are used to calibrate brightness of different standard candles. Those calibrations play a fundamental role in the Hubble Constant value determination, and for all these studies it is important to properly take into account the effect of interstellar extinction. The maps show clumpy and filamentous nature of dust clouds, and provide higher values of the extinction towards both galaxies, that were previously estimated.

An appendix to the paper is here.

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